The lARC Monographs on the Evaluation of Carcinogenic Risks to Humans represent an international expert-consensus approach to carcinogen hazard identification. The long-term objective is to critically review and evaluate the published scientific evidence on carcinogenic hazards to which humans are exposed. These include chemicals, complex mixtures, physical agents, biological agents, occupational exposures, and lifestyle factors. National and international health agencies use the lARC Monographs as a source of scientific information and as the scientific basis for their actions to prevent exposure to known, probable, and possible carcinogens. Each lARC Monograph contains a critical review of the published scientific literature and an evaluation of the weight of the evidence that an agent can increase the risk of cancer. Agents are selected for evaluation based on evidence of human exposure and some evidence of carcinogenicity. Agents can be re-evaluated if significant new data become available. The program also collaborates on scientific workshops to determine how to make the best use of contemporary studies to identify agents that play a role in cancer development and to understand their mechanisms. The Preamble to each volume of lARC Monographs describes the principles and procedures that are followed, including the scientific criteria that guide the evaluations. Each lARC Monograph is developed by a Working Group of experts who conducted the original research, avoiding real or apparent conflicts of interests. Working Groups typically consist of 20-25 scientists from 8-12 countries, with expertise in cancer epidemiology, experimental carcinogenesis, and related disciplines. The Working Group meets to review and reach consensus on drafts prepared by the experts before the meeting, and to develop and reach consensus on the evaluations. Later, lARC scientists review the text and tables to ensure their scientific accuracy and clarity, and the volume is edited and published. Funds are requested to support two of the three volumes produced each year.